Personally, im leaning towards leveling my main twink. My logic to do so is driven by the fact that most of the iconic gf'd stuff i have in my bags isnt even bis right now and probably wont be in shadowlands. So therefore, all the special gear like AGM, lucky fishing hat, TF legion invasion, etc will ALWAYS be in my bags regardless if I stay 10 or not. You can also create "swag sets" to prove to others that you were part of the OG f2p community too.
Another huge factor is I want to continue to get honorable kills on my toon that already has 250k+. I feel like rerolling a twink just wont feel the same to me, nor do I want to que at 10 and be at a disadvantage against lvl 19 twinks. The power gap between 10-19 is 10x more drastic than 20-29
OH YEAH AND I HAVE THIS ITEM KNOWN AS PRECIOUS RIBBON. YOU BET UR ASS I WANT TO PLAY ON THAT TOON 24 7